[Monday] "Col. James Estill has here a notice that he will send an express to the States with letters from Pacific Springs. I found the wind today disagreeably cold. We kept to the hills all day and came to the river tonight for the first time today. I think that the Mts. to the N. west are rightly named the Wind river Mts., if the wind always blows in their vicinity as it has since we came in sight of them. In the afternoon it appears to come directly from the snows and out of the caverns of these white headed giants of the Rocky Mountains, where I have no doubt they manufacture it. Made 17 miles."
The river McKinstry mentioned is the Sweetwater and the company will actually cross South Pass early tomorrow (July 9). McKinstry also mentions experiencing diarrhea and a severe toothache during the night of July 8.
The map below shows the actual location of South Pass, WY.